Cigarette smoking causes approximately one in three cancer deaths. Although the empirical evidence suggests that genetic influences may account for a substantial proportion of the population variation in smoking behavior, there has been little research specifically aimed at identifying genetic risks that contribute to different aspects of smoking behavior. This K07 award resubmission will support four research aims: 1) testing for genetic influence s on different aspects of smoking behavior, using newly developed models to examine the overlap versus specificity of genetic influences on different aspects of smoking behavior; 2) examining the relationship between genetic influences on smoking and genetic influences on depression and anxiety disorders; 3) determining how genetic influences on antisocial personality disorder (or conduct disorder) versus genetic influences on depression and anxiety disorders, contribute to risk of different aspects of smoking; 4) piloting the collection of twin pair data to test key assumptions of the Transtheoretical Model as they apply to smoking cessation versus persistence. These specific aims will be addressed by both secondary data analysis using existing large community-based twin samples and new pilot data collection built upon an existing research program by interviewing young adult twins (born 1968-1974). The pilot data will provide preliminary results to address key questions that cannot be addressed using the existing twin databases and set the groundwork for a longitudinal genetic epidemiology study of smoking cessation. The candidate's ultimate goals are to understand the etiology of smoking cessation and the genetic pathways leading to successful smoking cessation, to become an independent investigator in tobacco control, and to develop the expertise to mentor future scientists. To achieve these goals, this K07 award will allow the candidate to pursue specialized training and additional mentoring through structured coursework or workshops and didactic tutorials in the following areas: i) conducting large-scale epidemiologic twin studies; ii) molecular genetics and genomics; iii) extending expertise in advanced biometric modeling (incorporating genotyping and phenotyping information in a unified framework) and statistical genetics (genetic association methods); iv) broader aspects of epidemiologic and prevention research in cancer control.